With the removal of Prime Minister Srettha Thavisin from office by a court ruling after less than a year in power, Thailand has been thrown into political turmoil once again.

Reading the constitutional court’s decision on Wednesday, judge Punya Udchachon, said the judges ruled 5-4 in favour of dismissing Srettha of the Pheu Thai Party, as he had shown “no honesty and breached ethical standards” by appointing someone with a criminal conviction to his cabinet.

Udchachon said the real estate tycoon had failed to perform his duty with integrity and “grossly” violated ethics as he must have known about former lawyer Pichit Chuenban’s criminal record when he appointed him as a minister in his office in a cabinet reshuffle in April.

Pichit, who was jailed for six months in 2008 for attempting to bribe court officials with 2 million baht ($55,218) placed in a paper grocery bag, resigned from the post in May in an attempt to protect Srettha.

But that month, constitutional court judges voted 6-3 to accept a petition submitted by 40 senators to remove Srettha from office. Wednesday’s ruling came at the end of their investigation into the allegations.

Srettha’s dismissal means he is Thailand’s fourth prime minister in 16 years to be removed following rulings by the constitutional court.

He told reporters outside his office that while he “respect[ed] the verdict”, he was “sad” to be labelled dishonest.

The decision came as a surprise to many in Thailand, according to Khemthong Tonsakulrungruang, a lecturer in the faculty of political science at Thailand’s Chulalongkorn University.

“Most speculated that Srettha would be acquitted, so it’s a big shock that I don’t think many people were prepared for,” he told Al Jazeera. “The accusation itself is very trivial. [Appointing Pichit] is a bad political decision, for sure, but to say that he is acting in a dishonest or criminal way, that’s too far for most people.”

Khemthong said the ruling shows “no office is secure in this country” and “there’s always some legal pitfall that anyone can fall into”.

Who could replace Srettha?

Pheu Thai is now scrambling to firm a replacement candidate, with the Thai parliament to convene a special session to vote on the issue at 10am (03:00 GMT) on Friday.

The party can choose only those who were nominated as prime ministerial candidates prior to the 2023 election.

Ken Mathis Lohatepanont, a Thai political commentator and PhD candidate in the department of political science at the University of Michigan, told Al Jazeera that 75-year-old former Pheu Thai justice minister Chaikasem Nitisiri was currently the favourite to get the nod.

Another leading contender is 37-year-old Pheu Thai leader Paetongtarn Shinawatra, the daughter of former Prime Minister Thaksin Shinawatra and niece of Yingluck Shinawatra, also a former prime minister. Thaksin was removed in a military coup in 2006, and Yingluck in 2014.

Lohatepanont described Chaikasem, who was a prime ministerial candidate for Pheu Thai in 2019 and 2023, as a “dark horse”, with reports of his ill health meaning few had considered him as a potential leader. But with his condition reportedly improving in recent months, the veteran politician is now a “logical choice for Pheu Thai”.

“[Chaikasem] keeps the heat off Paetongtarn, who many see as either too inexperienced or too valuable to Thaksin to risk at this fraught juncture,” Lohatepanont said.

“[He also] keeps the premiership with Pheu Thai itself, without having to allow another party such as Bhumjaithai to take over the government’s leadership,” he added, referring to another major party in the Pheu Thai-led coalition.

Other members of the coalition, which came to power in controversial circumstances a year ago, will also field candidates. Not all are expected to do so, however, and negotiations will be held between parties as political backing is exchanged for cabinet positions.

If, as currently seems most likely, the coalition puts forward a Pheu Thai candidate and that candidate receives parliament’s backing, Lohatepanont said the “government will almost certainly remain [the same]”.

“Fundamentally, there is likely to be a fair amount of personnel and policy continuity,” he said.

Party manoeuvres

Srettha’s removal was the second significant ruling by Thailand’s constitutional court in a week, after it dissolved the Move Forward Party (MFP) on August 7. The judges ruled that the progressive party had violated the country’s constitution with its proposed reforms to Section 112 of Thailand’s Criminal Code, which restricts criticism of the monarchy.

The MFP won a shock election victory in Thailand’s 2023 general election, campaigning on a progressive platform that galvanised younger voters. Winning 151 seats in Thailand’s 500-seat House of Representatives, 10 more than second-placed Pheu Thai, MFP attempted to form a coalition with other pro-democracy parties.

But, using power handed to it by a 2017 military-drafted constitution, the military-installed Senate blocked MFP from power, while its leader Pita Limjaroenrat was suspended as an MP and barred from becoming prime minister.

Pheu Thai subsequently formed its own 11-party coalition under Srettha, incorporating government and military-aligned parties and excluding the MFP. The move was viewed by many as a betrayal of the pro-democracy movement, after Srettha broke a campaign promise to not work with the military-aligned Phalang Pracharat and United Thai Nation parties.

Their inclusion in the coalition was believed to have been part of a political deal struck to reduce the prison time facing Pheu Thai founder Thaksin, who returned to Thailand in 2023 after 15 years in self-imposed exile evading royal defamation charges.

Khemthong pointed to Thaksin, who was again indicted for royal defamation in June, as one possible explanation for the constitutional court’s surprising ruling against Srettha. He said people have speculated the move is a “rebuff to Thaksin” and there could be some “internal politics at play”.

Either way, he described Thaksin as “being held hostage” in this situation, meaning Pheu Thai was unlikely to challenge the ruling.

“Thaksin can’t leave the country, and so his bail can be revoked and he can be physically imprisoned at any minute, so there’s a big constraint on him,” he said.

Last week’s ruling by the constitutional court confirmed MFP’s swift downfall, mirroring what happened to its predecessor Future Forward after its strong showing in the 2019 elections. The ruling dissolved the party and banned its executive board, including Pita and current chief Chaithawat Tulathon, from politics for 10 years.

But 143 of the party’s lawmakers were able to keep their parliamentary seats by shifting to the Thinkakhao Chaowilai Party and renaming it the People’s Party. Rangsiman Rome, one such former MFP member, and now People’s Party MP, told Al Jazeera that Wednesday’s ruling against Srettha was a “coup by the court”.

He added that Move Forward was interested in working with Pheu Thai in order to “stop this madness”, referring to the military and ruling elite’s meddling in politics.

“This should be a good chance for us to reconsider the constitution, our constitution that was written by the coup maker,” he said, referring to the 2017 bill, drafted by army chief turned Prime Minister Prayuth Chan-ocha.

Rome said the People’s Party MPs would gauge the mood among Pheu Thai members in parliament on Friday. But he cautioned that given the serious criminal cases hanging over Thaksin, he was not optimistic about a new alliance being formed.

“If Pheu Thai tries to challenge the power in Thailand, I’m not sure they can have a free view when Thaksin has a case like this,” he said.